School-related COVID outbreaks are increasing in Michigan but you might not know that by looking at the data.
That’s because the Michigan Department of Health and Human Services on Monday changed how it defines a school outbreak.
The change could decrease the number of outbreaks reported and make it more difficult to track Michigan outbreaks over time.
Until now, two COVID cases associated with a school constituted an outbreak, but this week the agency increased the threshold to three. In addition, the state has begun counting as outbreaks instances where at least 10% of teachers and students in a specified group contract COVID through transmission linked to the school.
That’s in accordance with the definition of outbreak used by the Council of State and Territorial Epidemiologists, which recommended in an August report that states standardize outbreak reporting.
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Health Department spokesperson Lynn Sutfin acknowledged that “the new outbreak definition threshold may exclude some circumstances, which previously met the definition.”
For example, an outbreak reported last week at Berrien Springs Middle School in southwest Michigan would not have been reported this week because it involved only two students.
The department began using the new definition on Monday. It will not adjust historical data to conform to the new definition, Sutfin said.
“It makes sense to think about how to have consistency across states so we can make comparisons about COVID spread and outbreaks across states, however it will make it much more difficult for people to track the trajectory across time in Michigan,” said Katharine Strunk, director of the Education Policy Innovation Collaborative at Michigan State University.
EPIC has been studying how in-person learning contributes to the spread of COVID.
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“The danger in doing this midstream is that people who are not aware of the change will assume outbreaks have been reduced when they have not,” Strunk said. “It may lead people to make false assumptions about safety inside the school building.”
That’s a problem because people are using outbreak data to decide on mitigation strategies such as whether to send their children to school with masks, she said.
Of 297 Michigan school outbreaks reported in the last 30 days, 40 would not have been reported under the new definition.
Leaders of the epidemiologists’ council did not respond to questions Tuesday but their August report explained that consistent data is necessary “to characterize the epidemiology of the disease in the school setting, to measure the burden of disease in the school setting, and to inform public health action, including monitoring the impact of vaccination.”